Japanese Patent Application Publication No. 2010-169484 discloses a sample processing system including: a smear preparation apparatus that prepares a smear by dropping a blood sample onto a microscope slide; a smear imaging apparatus that captures an image of the smear prepared by the smear preparation apparatus and processes the captured image; and a smear transport apparatus that transports the microscope slide smeared with the blood from the smear preparation apparatus to the smear imaging apparatus. The smear imaging apparatus includes a microscope unit. The microscope unit includes a chuck unit. The chuck unit holds the microscope slide transported by the smear transport apparatus, and sets the microscope slide to an XY stage. Next, the microscope unit moves the XY stage in an X direction and a Y direction, and executes an operation of detecting white blood cells in the blood smeared on the microscope slide with a line sensor. Upon detection of a white blood cell, the microscope unit executes an autofocus operation of adjusting the focus of an objective lens, and captures an image of the white blood cell with a CCD camera. When the next microscope slide is transported by the smear transport apparatus to the smear imaging apparatus, the microscope unit executes another image capture operation in the same procedure.